This is from the RB manual but also applies to BiaB from what I can tell.

Quote:
Drum/Patch Map

This feature provides the ability to load a Drum/Patch Map file that is customized to your MIDI sound source. A Drum/Patch Map file has the .DK extension. These are the same files that are used by Band-in-a-Box to identify and use all the sounds and patches available on a given sound source or synth. Once a .DK file is loaded you can use the Re-map Drums/Patches command to re-map a General MIDI file to the custom sounds accessible in your .DK file. Check the PG Music web site for additional .DK files that may be applicable to your synth or sound source.


This page does have some DK files from users.
https://www.pgmusic.com/support_miscellaneous.htm

Many users go here for Patch maps, but there are also drum mapping files.
If you go to Options - MIDI Patch Files, etc you'll see an option to load up one of the .DK files in BiaB.

Unfortunately you are on your own after that as far as I can help. I've never actually done it in years.

I do not work here, but the benefits are still awesome
Make your sound your own!